Sheath system for catheter pump

ABSTRACT

A catheter pump assembly is provided. The catheter pump assembly includes a proximal portion, a distal portion, a catheter body having a lumen extending along a longitudinal axis between the proximal and distal portions, an impeller disposed at the distal portion, and a stator disposed at a downstream location of the impeller to straighten flow downstream from the impeller. The stator is collapsible from a deployed configuration to a collapsed configuration.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 15/840,117, filed on Dec. 13, 2017, which is a continuation of U.S. application Ser. No. 13/801,833, filed on Mar. 13, 2013, which claims the benefit of U.S. Provisional Application No. 61/646,789, filed on May 14, 2012, all of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

This application is directed to a catheter pump for mechanical circulatory support of a heart, and related components, systems and methods. In particular, this application is directed to reliable coupling of components that are subject to dynamic loads applied between a plurality of catheter bodies.

Description of the Related Art

Heart disease is a major health problem that has high mortality rate. Physicians increasingly use mechanical circulatory support systems for treating heart failure. The treatment of acute heart failure requires a device that can provide support to the patient quickly. Physicians desire treatment options that can be deployed quickly and minimally-invasively.

Intra-aortic balloon pumps (IABP) are currently the most common type of circulatory support devices for treating acute heart failure. IABPs are commonly used to treat heart failure, such as to stabilize a patient after cardiogenic shock, during treatment of acute myocardial infarction (MI) or decompensated heart failure, or to support a patient during high risk percutaneous coronary intervention (PCI). Circulatory support systems may be used alone or with pharmacological treatment.

In a conventional approach, an IABP is positioned in the aorta and actuated in a counterpulsation fashion to provide partial support to the circulatory system. More recently minimally-invasive rotary blood pump have been developed in an attempt to increase the level of potential support (i.e. higher flow). Rotary pumps have become more common recently for treating heart failure. A rotary blood pump is typically inserted into the body and connected to the cardiovascular system, for example, to the left ventricle and the ascending aorta to assist the pumping function of the heart. Other known applications include pumping venous blood from the right ventricle to the pulmonary artery for support of the right side of the heart. An aim of acute circulatory support devices is to reduce the load on the heart muscle for a period of time, to stabilize the patient prior to heart transplant or for continuing support. Rotary blood pumps generally utilize an electric motor which drives an impeller pump at relatively high speeds. In the case where the pump is remote from the motor, for example where the impeller is in the body and the motor is outside the body, there is a need for a robust and reliable connection between the motor and the impeller. There may also be the need for forming a flexible connection between the motor shaft and the impeller to allow free movement of various pump components during use and when pushing through the vasculature to the treatment location. There is also the continuing need to provide these system components in a compact, efficient form factor to allow for percutaneous approaches.

There is a need for improved mechanical circulatory support devices for treating acute heart failure. Fixed cross-section ventricular assist devices designed to provide partial or near full heart flow rate are either too large to be advanced percutaneously (e.g., through the femoral artery without a cutdown) or provide insufficient flow.

SUMMARY OF THE INVENTION

An aspect of at least one of the embodiments disclosed herein is the realization that the connection of a flexible proximal body to a more rigid distal segment of a catheter assembly can be better secured with a robust mechanical interface between one or more features of these components. For example, a distal end of the flexible proximal body can be fitted with a device or structure providing an interface that mechanically engages the flexible proximal body and that can be directly joined, e.g. welded, to a structure to which a load is applied.

In one embodiment, a catheter pump assembly is provided that includes an elongate polymeric catheter body, a cannula, and a tubular interface. The elongate polymeric catheter body has a proximal end and a distal end. The cannula has an expandable portion disposed distally of the elongate polymeric catheter body. The cannula can also have another tubular portion that is proximal to the distal portion. The tubular interface has an outer surface configured to be joined to the tubular portion of the cannula and an inner surface. The inner surface is disposed over the distal end of the elongate polymeric catheter body. The tubular interface has a plurality of transverse channels extending outward from the inner surface of the tubular interface. An outer surface of the elongate polymeric catheter body projects into the transverse channels to mechanically integrate the elongate polymeric catheter body with the tubular interface.

In another embodiment, a catheter pump assembly is provided that includes an elongate polymeric catheter body, a tubular member, and a mechanical interface. The elongate polymeric catheter body has a proximal end and a distal end. At least a portion of the tubular member is disposed distally of the elongate polymeric catheter body. The mechanical interface is disposed between a portion of the elongate polymeric catheter body and the tubular member. The mechanical interface is configured to mechanically integrate with a surface of the elongate polymeric catheter body.

In another embodiment, a catheter pump assembly is provided that includes an elongate catheter body, a metallic tubular member, and first and second mechanical interfaces. The elongate catheter body has a proximal portion and a distal portion. The metallic tubular member is disposed at least partially distally of the elongate catheter body. The first mechanical interface has a first portion joined to the distal portion of the elongate catheter body and a second portion welded to the metallic tubular member. The second mechanical interface is disposed on an outside surface of the catheter pump assembly. The second mechanical interface has a deflectable member configured to be disposed adjacent to the outside surface of the catheter pump assembly in a first configuration. The deflectable member is configured to be disposed inward of the outside surface of the catheter pump assembly in a second configuration. When in the second configuration, the deflectable member mechanically and securely engages the outside surface of the catheter pump assembly with a structure disposed inward of the second mechanical interface.

In another embodiment, a method is provided for coupling components of a catheter pump assembly together. An elongate polymeric tubular body is provided that has a proximal end and a distal end. A metallic tubular body is provided that has a proximal portion and a distal portion. A mechanical interface having a first interface zone and a second interface zone is positioned such that the first interface zone is disposed over a portion of the elongate polymeric tubular body adjacent to the distal end thereof. The polymer is then caused to flow into the first interface zone, whereby the elongate polymeric tubular body becomes joined with the first interface zone of the mechanical interface. The metallic tubular body is coupled with the second interface zone of the mechanical interface.

In one approach, the polymer is caused to flow by heating the elongate polymeric tubular body to cause at least a portion of elongate polymeric tubular body adjacent to the distal end thereof to transition to a state with low resistance to deformation.

In another embodiment, a catheter pump assembly is provided that includes a proximal portion, a distal portion, and a catheter body having a lumen extending therebetween along a longitudinal axis. The catheter pump assembly also includes a torque assembly that has a first portion disposed in the lumen of the catheter body and a second portion disposed distal of the first portion. The second portion coupled with an impeller. The torque assembly causes the impeller to rotate upon rotation of the first portion of the torque assembly. The catheter pump assembly also includes a thrust bearing and a thrust bearing brace. The thrust bearing is disposed within the catheter pump assembly adjacent to the distal end of the catheter body. The thrust bearing resists movement of the torque assembly along the longitudinal axis. The thrust bearing brace is disposed on the outside surface of the torque assembly. The thrust bearing brace has a distal face that is directly adjacent to a proximal face of the thrust bearing.

In another embodiment, a catheter assembly is provided that includes an elongate flexible body, a torque assembly, a bearing assembly, and a sleeve. The elongate flexible body is disposed along a proximal portion of the catheter assembly and has a proximal infusate channel formed therein. The torque assembly extends through the elongate flexible body. The bearing assembly comprises a housing having an outer surface and a bearing surface disposed within the housing. The bearing surface provides for rotation of the torque assembly within the bearing housing. The sleeve comprises and an inner surface configured to be disposed over the outer surface of the housing of the bearing assembly and a fluid communication structure that extends through the walls of the sleeve. The catheter assembly also includes a distal infusate channel in fluid communication with the proximal infusate channel, the distal infusate channel disposed over the outer surface of the bearing housing and through side walls of the slot.

In another embodiment, a catheter pump assembly is provided that includes a proximal portion, a distal portion, and a catheter body having a lumen extending along a longitudinal axis between the proximal and distal portions. The catheter pump assembly also includes an impeller disposed at the distal portion and a stator disposed distal of the impeller to straighten flow downstream from the impeller. The stator is collapsible from a deployed configuration to a collapsed configuration.

In another embodiment, a catheter system is provided that includes an elongate polymeric catheter body, a cannula, and at least one expandable component disposed within the cannula. The elongate polymeric catheter body has a proximal end and a distal end. The cannula has an expandable portion disposed distally of the elongate polymeric catheter body. The catheter system also includes an elongate sheath body that has a retracted position in which the elongate sheath body is proximal of the expandable portion of the cannula and the at least one expandable component and a forward position in which the elongate sheath body is disposed over the expandable portion of the cannula and the at least one expandable component. A first segment of the elongate sheath body disposed over the expandable portion of the cannula and the at least one expandable component is configured to resist kinking to a greater extent than a second segment of the elongate sheath body disposed adjacent to the first segment.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the subject matter of this application and the various advantages thereof can be realized by reference to the following detailed description, in which reference is made to the accompanying drawings in which:

FIG. 1 illustrates one embodiment of a catheter pump configured for percutaneous application and operation;

FIG. 2 is a plan view of one embodiment of a catheter adapted to be used with the catheter pump of FIG. 1;

FIG. 3 show a distal portion of the catheter system similar to that of FIG. 2 in position within the anatomy;

FIG. 4 is a perspective view of a distal portion of a catheter assembly according to one embodiment;

FIG. 5 is a perspective partial assembly detail view of a portion of the catheter assembly of FIG. 4.

FIG. 6 is a cross-sectional view of a portion of a connection zone of the catheter assembly of FIG. 4.

FIG. 6A is a schematic view of embodiments of an outer sheath configured to enhanced delivery and retrieval performance.

FIG. 7 is a perspective view of a distal portion of a catheter assembly according to another embodiment;

FIG. 8 is a perspective partial assembly detail view of a portion of the catheter assembly of FIG. 7;

FIG. 9 is a detail view of a mechanical interface of a catheter assembly;

FIG. 10 is a cross-sectional view of a portion of a connection zone of the catheter assembly of FIG. 9;

FIGS. 11-14 illustrate features of additional embodiments of catheter assemblies having robust mechanical interface; and

FIGS. 15-17 illustrate features of additional embodiments of catheter assemblies having robust mechanical interface.

More detailed descriptions of various embodiments of components for heart pumps useful to treat patients experiencing cardiac stress, including acute heart failure, are set forth below.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A high performance catheter pump is desired to provide sufficient output to approach and in some cases exceed natural heart output. Performance of this nature can be achieved with inventive components disclosed herein.

FIGS. 1-3 show aspects of a catheter pump 10 that can provide high performance including flow rates similar to full cardiac output. The pump 10 includes a motor driven by a controller 22. The controller 22 directs the operation of the motor 14 and an infusion system 26 that supplies a flow of infusate in the pump 10. A catheter system 80 that can be coupled with the motor 14 houses an impeller within a distal portion thereof. In various embodiments, the impeller is rotated remotely by the motor 14 when the pump 10 is operating. For example, the motor 14 can be is disposed outside the patient. In some embodiments, the motor 14 is separate from the controller 22, e.g., to be placed closer to the patient. In other embodiments, the motor 14 is part of the controller 22. In still other embodiments, the motor is miniaturized to be insertable into the patient. Such embodiments allow the drive shaft to be much shorter, e.g., shorter than the distance from the aortic valve to the aortic arch (about 5 mm or less). Some examples of miniaturized motors catheter pumps and related components and methods are discussed in U.S. Pat. Nos. 5,964,694; 6,007,478; 6,178,922; 6,176,848; and all of which are hereby incorporated by reference herein in their entirety for all purposes.

FIG. 3 illustrates one use of the catheter pump 10. A distal portion of the pump 10 is placed in the left ventricle LV of the heart to pump blood from the LV into the aorta. The pump 10 can be used in this way to treat patients with a wide range of conditions, including cardiogenic shock, myocardial infarction, and acutely decompensated heart failure, and also to support a patient during a procedure such as percutaneous coronary intervention. One convenient manner of placement of the distal portion of the pump 10 in the heart is by percutaneous access and delivery using the Seldinger technique or other methods familiar to cardiologists. These approaches enable the pump 10 to be used in emergency medicine, a catheter lab and in other non-surgical settings.

FIG. 2 shows features that facilitate small blood vessel percutaneous delivery and high performance up to and in some cases exceeding normal cardiac output in all phases of the cardiac cycle. In particular, the catheter system 80 includes a catheter body 84 and a sheath assembly 88. An impeller assembly 92 is coupled with the distal end of the catheter body 84. The impeller assembly 92 is expandable and collapsible. In the collapsed state, the distal end of the catheter system 80 can be advanced to the heart. In the expanded state the impeller assembly 92 is able to pump blood at high flow rates. FIGS. 2 and 3 illustrate the expanded state. The collapsed state can be provided by advancing a distal end 94 of an elongate body 96 distally over the impeller assembly 92 to cause the impeller assembly 92 to collapse. This provides an outer profile throughout the catheter assembly 80 that is of small diameter, for example 12.5 French as discussed further below.

In some embodiments, the impeller assembly 92 includes a self-expanding material that facilitates expansion. The catheter body 84 on the other hand preferably is a polymeric body that has high flexibility. When the impeller assembly 92 is collapsed, as discussed above, high forces are applied to the impeller assembly 92. These forces are concentrated at a connection zone, where the impeller assembly 92 and the catheter body 84 are coupled together. These high forces, if not carefully managed can result in damage to the catheter assembly 80 and in some cases render the impeller within the impeller assembly 92 inoperable. A reliable mechanical interface is provided to assure high performance. While this interface is extremely beneficial for an assembly with an expandable impeller disposed in an expandable cannula, it also applies to assemblies including a fixed diameter impeller, which may be disposed in an expandable cannula or even in a non-expandable portion in fluid communication with an expandable cannula. In one variation, the impeller is disposed proximal of an expandable cannula in a rigid segment (e.g., a pump ring) and an expandable cannula is provided. The mechanical interfaces and inner and outer sheath assemblies facilitate the collapse of the cannula in such embodiments. A further design permits the impeller to be withdrawn into a rigid structure, e.g., a pump ring, to collapse the impeller before the cannula is collapsed.

The mechanical components rotatably supporting the impeller within the impeller assembly 92 permit high rotational speeds while controlling heat and particle generation that can come with high speeds. The impeller may be rotated as speeds above 6000 RPM, above 9000 RPM, above 10,000 RPM, above 15,000 RPM, above 20,000 RPM, above 25,000 RPM, or above 30,000 RPM. The infusion system 26 delivers a cooling and lubricating solution to the distal portion of the catheter system 100 for these purposes. However, the space for delivery of this fluid is extremely limited. Some of the space is also used for return of the infusate. Providing secure connection and reliable routing of infusate into and out of the catheter assembly 80 is critical and challenging in view of the small profile of the catheter body 84.

Various aspects of the pump and associated components are similar to those disclosed in U.S. Pat. Nos. 7,393,181; 8,376,707; 7,841,976; 7,022,100; and 7,998,054, and in U.S. Pub. Nos. 2011/0004046; 2012/0178986; 2012/0172655; 2012/0178985; and 2012/0004495, the entire contents of each of which are incorporated herein for all purposes by reference. In addition, this application incorporates by reference in its entirety and for all purposes the subject matter disclosed in each of the following concurrently filed applications: application Ser. No. 13/802,556, which corresponds to attorney docket no. THOR.072A, entitled “DISTAL BEARING SUPPORT,” filed on Mar. 13, 2013; Application No. 61/780,656, which corresponds to attorney docket no. THOR.084PR2, entitled “FLUID HANDLING SYSTEM,” filed on Mar. 13, 2013; application Ser. No. 13/802,570, which corresponds to attorney docket no. THOR.090A, entitled “IMPELLER FOR CATHETER PUMP,” filed on Mar. 13, 2013; application Ser. No. 13/801,528, which corresponds to attorney docket no. THOR.092A, entitled “CATHETER PUMP,” filed on Mar. 13, 2013; and application Ser. No. 13/802,468, which corresponds to attorney docket no. THOR.093A, entitled “MOTOR ASSEMBLY FOR CATHETER PUMP,” filed on Mar. 13, 2013.

FIGS. 4-6 show a first embodiment of a working end of a catheter assembly 100 forming a part of one embodiment of the catheter pump 10. The catheter assembly 100 is similar to the catheter system 84 except as discussed differently below. The catheter assembly 100 includes an elongate catheter body 104. A proximal end of the catheter body 104 can be coupled with a motor housing. A distal portion of the catheter body 104 is coupled to a cannula 108 configured to house a high flow rate impeller 112. The exemplary catheter pump can be configured to produce an average flow rate of 4 liters/minute or more at physiologic conditions, e.g., at the typical systolic pressure of a patient needing treatment, such as 60 mmHg. In various embodiments, the pump can be configured to produce a maximum flow rate (e.g. low mm Hg) of greater than 4 Lpm, greater than 4.5 Lpm, greater than 5 Lpm, greater than 5.5 Lpm, greater than 6 Lpm, greater than 6.5 Lpm, greater than 7 Lpm, greater than 7.5 Lpm, greater than 8 Lpm, greater than 9 Lpm, or greater than 10 Lpm. In various embodiments, the pump can be configured to produce an average flow rate at 60 mmHg of greater than 2 Lpm, greater than 2.5 Lpm, greater than 3 Lpm, greater than 3.5 Lpm, greater than 4 Lpm, greater than 4.25 Lpm, greater than 4.5 Lpm, greater than 5 Lpm, greater than 5.5 Lpm, or greater than 6 Lpm.

In some embodiments both the cannula 108 and the impeller 112 are actuatable from a first configuration for delivery through a patient to a working site to a second configuration for generating high flow at the working site. The first configuration may be a low profile configuration and the second configuration may be an expanded configuration. The low profile configuration preferably enables access via a femoral artery or other peripheral blood vessel without excessive obstruction of blood flow in the vessel, as discussed further below.

The catheter body 104 preferably has a plurality of lumens, including a first lumen 140 adapted for housing a drive shaft 144, a second lumen 140B for conveying a medical fluid distally within the catheter body 104, and a third lumen 140C for anchoring a bearing housing 146 to the catheter body 104. The drive shaft 144 extends proximally within the catheter body 104 from the impeller 112. The drive shaft 144 couples with the motor at the proximal end and with the impeller 112 at the distal end thereof. The drive shaft 144 can be formed with any suitable structure, but should be sufficient flexible to traverse at least from a peripheral (e.g., femoral) artery to a heart chamber, such as the left ventricle, as well as sufficiently durable to rotate at a high speed for several hours, for several days, and in some cases, months. The drive shaft 144 can be coupled with an impeller assembly 112 including an expandable impeller 112A) disposed on a tubular body 112B FIGS. 4 and 6 shows these structures. The impeller 112A preferably includes an elastomeric polymer structure that can be formed as a unitary body. The tubular body 112B can be a metal hypotube. The tubular body 112B can be received in a distal portion of the drive shaft 144.

Any suitable material or combination of materials can be used for the catheter body 104 or catheter bodies 104A and 304 discussed below and provided in some embodiments. In one embodiment, the catheter body 104 has an inner layer 148 surrounding the lumen 140 that comprises high density polyethylene (HDPE). For example, Marlex 4903 HDPE can be disposed about the lumen 140. If a composite structure is used to form the catheter body 104, the inner layer 148 has a thickness that is sufficient to withstand wear caused by interaction with the drive shaft 144, which can be rotated at a very high speed in some applications, for example from 20,000-40,000 revolutions per minute. The inner layer can have a thickness of 0.003 inches.

The second lumen 140B extends from a proximal end in fluid communication with a source of infusate, which can be a medical fluid (e.g., saline), to a distal end adjacent to the impeller assembly 112. For example, the second lumen 140B can have an outlet disposed adjacent to a flow channel formed in or about the bearing housing 146. Examples of bearing housing flow channels are shown in FIGS. 5, 10, and in application Ser. No. 13/343,618, which is hereby incorporated by reference. In one embodiment of the catheter body 104A, the second lumen 140B is generally circumferentially elongated, for example having two sides that are curved with an arc length of about 0.030 inches and two sides that are straight, disposed along a radial direction of the catheter body 104 and about 0.010 inches in length. A proximal end of the second lumen 140B is coupled with a port, which may be similar to the luer 145 in FIG. 2, or other fluid connection device. Any suitable connection between a port and lumen can be used, e.g., a skived connection can be used.

The third lumen 140C can be used to enhance the security of the connection between the catheter body 104, 104A and the bearing housing 146. For example, the third lumen 140C can be sized to receive a plurality of, e.g., two, pull wires 160. The pull wires 160 can take any suitable form, but preferably are sized to be easily received within the lumen 140C. In one embodiment, the lumen 140C is spaced apart from but about the same size as the second lumen 140B and the pull wires are generally rectangular in shape, e.g., having a thickness of about 0.005 inches and a width of about 0.010 inches. The pull wires 160 can be formed of any material that is sufficiently rigid in tension, e.g., of stainless steel with pull strength of at least about 300 ksi. In one arrangement, the pull wires 160 extend at least about three inches into the elongate body 104 in the third lumen 140C and extend out of the third lumen 140C to overlay the bearing housing 146 as shown in FIG. 5.

FIG. 6 shows one approach to compactly arranging the pull wires 160 and structure coupled together thereby. In particular, a proximal portion 160A of the wires is received within a distal length of the third lumen 140C and a distal portion 160C of the wires is disposed distal of the catheter body 104. A transition 160B is provided between the zones 160A, 160C causing the proximal portion 160A to be disposed closer to the longitudinal axis of the impeller catheter assembly 100 than is the distal portion 160C. This permits the outer surface of the catheter body 104 to be closer to the longitudinal axis of the catheter assembly 100 than if the pull wires were straight with the distal portion 160C in the same position as illustrated.

Providing a plurality of pull wires provides redundancy in the connection between the catheter body 104, 104A and the bearing housing 146. In some cases, this redundancy is not needed and a single wire can be used. The redundancy is beneficial, however, because substantial tension force is applied at this connection point when the expandable cannula 108 is collapsed. In one technique relative motion is provided between the catheter body 104, 104A and an outer sheath disposed over the catheter body until the outer sheath slides over a proximal portion of the cannula 108. Further relative motion causes the cannula 108 to be compressed, but not without a substantial force being applied thereto. This force is born at several points, including at the junction between the catheter body 104, 104A and the bearing housing 146. Disconnection of the bearing housing 146 would be problematic, requiring complex procedures to extract the disconnected distal working end of the catheter assembly 100.

The pull wires 160 preferably are located close together on the same side of the catheter body 104, 104A. This arrangement enhances bending flexibility, which is beneficial if tortuous vasculature must be traversed to deliver the catheter assembly 100 to a treatment site, e.g., a heart chamber. FIGS. 12-14 illustrate other techniques for enhancing the security of the connection of the bearing housing 146 to a catheter body.

In some embodiments, placing a radiopaque marker on a distal portion of the catheter assembly 100 is advantageous to confirm the location of the working end, e.g., of the cannula 108 and/or impeller 112 prior to and/or after deployment.

Gross mechanical properties of the catheter body 104 can be varied along the length thereof to provide appropriate flexibility and maneuverability within the vasculature to facilitate delivery and operation of the catheter pump into which the catheter assembly 100 is incorporated. For example, in one embodiment, the catheter body 104 is stiffest near the distal end where the catheter body 104 is joined to the working end. In one embodiment, a distal section of the catheter body 104 comprises a material, such as Pebax, having a hardness of about 72D. A proximal section of the catheter body 104 comprises a material, such as Vestamid having a hardness greater than about 72D. Between these relatively hard sections ends, a middle section of the catheter body comprises a material having a lower hardness, e.g., MX1205 Pedbax. The low hardness section provides a softer structure in the vicinity of the aortic arch, where the catheter will be consistently resting on the vessel wall. One or more intermediate hardness sections can be provided between the distal, proximal and middle sections. These arrangements are also relevant to the other inner catheter bodies discussed herein, including bodies 104A, 304.

Alternately, or in addition to these features, the catheter body 104 can have different diameters along its length to provide several important performance benefits. The diameter of a proximal portion of the catheter body 104 can be relatively large to enhance pushability and trackability of the catheter assembly 100. The diameter of a distal portion of the catheter body 104 can be relatively small to enhance flexibility of the distal tip and also to match the profile of the bearing housing 146 such that the lumens 140B align with flow channels at least partly defined by the bearing housing (e.g., the slots 220 discussed below). The enlarged diameter and enhanced hardness at the proximal end both contribute to the maneuverability of the catheter assembly 100. These arrangements are also relevant to the other inner catheter bodies discussed herein, including bodies 104A, 304 and the catheter assemblies 100A, 300, and 400 (discussed below).

In addition to the foregoing structures for varying the stiffness along the length of the catheter body 104, a separate stiffening component, such as a braid 188, can be disposed in the catheter body 104, 104A. In one embodiment, a 0.001 inch by 0.003 inch flat wire of 304V stainless steel is embedded in the catheter body 104, 104A and the braid includes a 70 ppi configuration. The braid 188 can be positioned in any suitable location, e.g., between an inner layer 148 and an outer layer, as shown in FIG. 9 of the drawings.

As discussed above, the catheter assembly 100 preferably also includes an outer sheath or sheath assembly 88 provided over the elongate body 104, 104A to aid in delivering, deploying and/or removing the impeller 112. The outer sheath 88 can include an elongate body 96 comprising an inner surface surrounding a lumen disposed therein. The inner lumen can comprise a low friction material or layer. For example, a thickness of PTFE can be provided adjacent the inner lumen. In one embodiment, one or more separate materials can be provided at an outer surface of the elongate body 96.

The elongate body 96 preferably is connected at the proximal end with a proximal hub and/or a suitable connector, such as a Tuohy Borst connector. The proximal hub can include a luer fitting.

The outer sheath 88 also may have varied hardness or other gross mechanical properties along its length to provide appropriate flexibility and maneuverability within the vasculature to facilitate delivery and operation of the catheter pump into which the outer sheath is incorporated, and also to facilitate collapse of the cannula 108 after deployment thereof. FIG. 6A illustrates schematically bulk property variation in two embodiments of the sheath assembly 88. In particular, an elongate body extending between the proximal and distal ends of the sheath assembly 88 has different hardness at different locations along the length. The different hardnesses enhance the maneuverability of the sheath assemblies 88A, 88B to minimize kinking of the elongate body as the catheter assembly 100 is tracking toward the heart and/or when the elongate body is used to collapse an expandable cannula or impeller, as discussed elsewhere herein.

The elongate body of the sheath assembly 88A has a proximal portion “A” with a highest hardness. The proximal portion A can comprise vestamid or other similar material. A portion “B” distal of the proximal portion A and residing over a zone of the cannula in which the impeller I and the distal bearing support S (if present) are housed can have a hardness that is lower than that of the portion A. Portion B can comprise 55D pebax. A portion “C” disposed distal of the portion B can comprise a material with the lowest hardness of the elongate body of the sheath assembly 88A, e.g., can comprise MX1205. A portion “D” at the distal end of the elongate body of the sheath assembly 88A can have a relatively high hardness, e.g., 72D pebax. The sheath assembly 88A upon distal movement over the expanded cannula initially contacts the cannula with the relatively hard material of portion D. The relatively soft portion C may contact the vasculature as the catheter assembly 100 is advanced, and its relatively soft structure is biocompatible. Portion B has a hardness that is high enough to protect the zones I and S of the cannula, impeller, and support. Portion A is the hardest of the materials used in the sheath assembly 88A, to aid in maneuverability.

The elongate body of the sheath assembly 88B has a proximal portion and distal bearing zone portion “A” with a highest hardness. The proximal portion A can comprise vestamid or other similar material. A portion “B” between the proximal portion A and the distal bearing zone portion A. The portion B resides adjacent to the transition from the catheter body 104 to the cannula proximal portion 116 and can have a hardness that is lower than that of the portion A. Portion B can comprise 55D pebax. Portions C and D in the sheath assembly 88B are the same as in the sheath assembly 88A. A portion E is disposed between the portions A and C, e.g., distal of the portion A disposed over the distal bearing support. Portion E can include a series of progressively softer lengths, e.g., a first length of 72D pebax, a second length of 63D pebax, and a third length of 55D pebax. Other materials and hardnesses can be used that provide good resistance to kinking in the delivery of the catheter assembly 100 and/or in the process of re-sheathing the expanded cannula and impeller.

FIGS. 7-10 incorporate the discussion above and illustrate additional features and embodiments. FIGS. 7 and 9 illustrate aspects of a mechanical interface between a bearing housing 146A and the catheter body 104A. In particular, a coupler 200 is provided between the bearing housing 146A and the catheter body 104A. The coupler 200 (also shown in FIG. 6) is similar to the coupler 628 disclosed in U.S. application Ser. No. 13/343,618, which is hereby incorporated by reference herein. In this configuration a thrust bearing 204 is provided in the bearing housing 146A. In some embodiments, a thrust bearing brace 208 is disposed just proximal of the thrust bearing 204. The thrust bearing brace 208 can take any suitable form, but preferably provides a shoulder or other radial protrusion from the outer surface to the impeller shaft 112B that abuts a proximal face of the thrust bearing 204. The thrust bearing brace 208 minimizes or completely prevents movement of the thrust bearing 204 on the impeller shaft 112B. Such movement is possible because the impeller on the impeller shaft 112B generates significant distally oriented thrust. In some assemblies, the thrust bearing 204 is interference fit onto the impeller shaft 112B. When sized and fit properly, this connection maintains the relative position of thrust bearing 204 to the impeller shaft 112B under the thrust forces that are applied. The thrust bearing brace 208 provides redundancy of this connection. In one embodiment, the thrust bearing brace 208 comprises a short hypotube that is coupled with, e.g., laser welded to the impeller shaft 112B. The weld completely prevents relative axial movement between the impeller shaft 112B and the thrust bearing brace 208. The abutment between the trust bearing 204 and the thrust bearing brace 208 prevent relative movement between the thrust bearing 204 and impeller shaft 112B if the coupling between the impeller shaft 112B and the thrust bearing 204 loosens.

FIG. 8 shows that an outer surface of the bearing housing 146A can be covered by a cylindrical sleeve 216. The sleeve has at least one slot 220 formed therein. The slot 220 can be circumferentially aligned to or otherwise in fluid communication with the second lumen 140B such that infusate fluid flowing distally in the lumen enters the slot and can be directed distally in a space formed between the bearing housing 146A, the sleeve 216 and an outer sleeve, that may be a proximal portion 222 of the frame-like structure of the cannula 108. This structure is shown in FIGS. 4 and 5. In FIG. 4, the cannula 108 is displaced proximally to reveal the sleeve 216, which would be covered by a proximal cylindrical portion 222 of the cannula 108 when the catheter assembly 100 is assembled. A difference between the impeller assembly/catheter body interface of the embodiment of FIGS. 4-6 and the embodiment of FIGS. 7-11 is that the sleeve 216A includes recess 220A in fluid communication with the lumen 140B. The recesses 220A are fluid flow structures. Other ports into the inside of the bearing housing 146A can be accessed through apertures 224 that do not extend to the proximal end of the sleeve 216. The apertures are fluid communication structures through which fluid can flow into the bearing housing. Flow from the lumen 104B to the apertures 224 can be provided through a circumferential space defined between the outer surface of the sleeve 216 and an inner surface of the proximal portion 222 of the cannula 108. See FIG. 10. In some cases, the apertures 224 are additionally or alternately adapted to receive components of secondary mechanical interface discussed below. In other embodiments, troughs are formed in an outer surface of the bearing housing are enclosed by the inner surface of the sleeve 216 to form enclosed flow channels for infusate.

Catheter pumps incorporating the catheter assembly and variation thereof can be configured to deliver average flow rates of over 4 liters/minute for a treatment period. For example, a treatment period can be up to 10 days for acute needs, such as patient in cardiogenic shock. Catheter pumps incorporating the catheter assembly 100 or such modifications thereof can be used for shorter periods as well, e.g., for support during high risk catheter or surgical procedures.

Also, catheter pumps incorporating the catheter assembly 100 or modifications thereof can be used for left or right side heart support. Example modifications that could be used for right side support include providing delivery features and/or shaping a distal portion that is to be placed through at least one heart valve from the venous side, such as is discussed in U.S. Pat. Nos. 6,544,216; 7,070,555; and US 2012-0203056A1, all of which are hereby incorporated by reference herein in their entirety for all purposes. For example, the catheter assembly 100 or modifications thereof can be configured to be collapsed to be deliverable through a 13 French introducer sheath and can be expanded to up to 24 French when deployed. In one embodiment, the outer profile of the catheter assembly 100 or modifications thereof is approximately 12 French, but can be any size that is insertable into a femoral artery without requiring surgical cutdown. The catheter assembly 100 can be as large as 12.5 F to be inserted through a 13 French introducer sheath. One method involves deployment of the cannula 108, having an expandable nitinol structure, across the aortic valve. In this position, the impeller 112 can be disposed on the aorta side of the valve and a distal length of the cannula 108 within the ventricle.

In other embodiments, the outer profile of the catheter assembly 100 or modifications thereof is less than 12 French, e.g., about 10 French. The 10 French configuration can be useful for patients with lower flow needs, e.g., about 3 liters per minute or less at physiologic conditions. In another example, an 8 French configuration can be useful for patients with lower flow needs, e.g., about 2 liters per minute or less at physiologic conditions.

FIGS. 11-14 illustrate additional embodiments in which the structural integrity of a catheter assembly 300 is enhanced to provide security in connection with sheathing an expandable portion. FIG. 11 shows that a distal portion of the catheter assembly 300 includes components similar to those hereinbefore described. In particular, the catheter assembly 300 includes a catheter body 304, an expandable cannula 308 and an expandable impeller 312. The catheter body can take any suitable form. In one embodiment, the catheter body 304 has variable hardness along its length.

The cannula 308 includes a self-expanding structure enclosed in a polymeric film. The self-expanding structure can be a distal portion of a member having a non-expanding tubular portion 316 proximal of the self-expanding structure. The tubular portion 316 plays a role in anchoring the cannula 308 to the catheter body 304.

FIG. 11 shows that a support member 328 can be positioned within the cannula 308 to prevent unacceptable variance in the gap between the tip of the impeller 312 and the inside surface of the cannula. More details of this structure are set forth in concurrently filed application Ser. No. 13/802,556, which corresponds to attorney docket no. THOR.072A, entitled “DISTAL BEARING SUPPORT,” filed on Mar. 13, 2013, which is incorporated hereby by reference herein for all purposes. Successful collapse of the cannula 308, the impeller 312, and the support 328 focuses forces on a joint between the cannula 308 and the catheter body 304.

FIGS. 11-14 illustrate features that enhance the security of the connection catheter body 304 and the cannula 308. In FIG. 11, no separate structure is shown between the catheter body 034 and the non-expanding tubular portion 316. These structures are joined in other manners, such as indirectly by the force transfer capability of the pull wires discussed above and/or by an adhesive. In FIG. 12, the distal end of the catheter body 304 is coupled with a ferrule 336. The ferrule 336 is an example of a structure to mechanically join the catheter body 304 to the cannula 308. In one embodiment, the ferrule 336 includes a distal zone 340 for mechanically joining the ferrule 336 to the catheter body 304. The distal zone 340 is also configured to mechanically couple with the cannula 308, for example by welding. A plurality of apertures 344 is provided in one embodiment for mechanically joining the ferrule 336 to the catheter body 304. The apertures 344 enable the material of the catheter body 304 to extend into the distal zone 340. In one technique the ferrule 336 is disposed over the catheter body 304 which extends into the apertures 344.

The apertures 344 can be arranged in multiple zones. In one embodiment a first zone is disposed distally of the second zone. The first zone can be disposed adjacent to the distal end of the ferrule 336 and the second zone is disposed proximal of the first zone. The first zone can include four apertures 344A spaced evenly about the periphery of the body of the ferrule. The second zone can include a plurality of (e.g., four) apertures 344B spaced evenly about the periphery of the body of the ferrule 336. A specific advantageous embodiment provides four apertures 344B in the second zone. The apertures 344B of the second zone can be spaced evenly about the body of the ferrule 336. Preferably the apertures 344 of the first and second zones are offset to provide a great deal of redundancy in the security of the connection of the catheter body 304 to the ferrule 336. For example, the apertures 344 in the first and second zones can be offset by one-half the circumferential distance between adjacent apertures 344.

The ferrule 336 also includes a proximal zone 348 disposed proximally of the aperture 344. The proximal zone 348 preferably is configured to provide an excellent fluid seal between the ferrule and the non-expandable tubular portion 316 of the cannula 308. In one embodiment, the proximal zone 348 includes a plurality of recesses 352 in the outer surface of the proximal portion 348. The recesses 352 can take any form consistent with good sealing, and in one embodiment the recesses are turns of a continuous helical groove in the outer surface of the ferrule 336. The helical groove is configured to receive a sealant that can bridge from the base of the grooves to the inner surface of the proximal portion 316 of the cannula 308. In one embodiment, the sealant includes an adhesive that can flow into the helical groove and be adhered to the inner surface of the proximal portion 316 of the cannula 308.

Although the weld and adhesive that can be formed or disposed between the ferrule 336 and the proximal portion 316 of the cannula 308 can provide excellent security between these components of the catheter assembly 300, a supplemental securement device 360 can be provided in some embodiments. FIG. 11 illustrates one embodiment in which a mechanical securement device 360 is provided. The mechanical securement device 360 includes a cantilevered member that can be deformed from the non-expandable proximal portion 316 of the cannula 308 into corresponding recesses disposed inward of the securement device.

In one embodiment, a recess 364 is provided within the catheter assembly 300 to receive the securement device 360. The recesses 364 can be formed in an internal structure disposed within the proximal portion 316. In a first variation, a sleeve 368 is provided immediately within the non-expandable proximal portion 316 of the cannula 308. The sleeve 368 is provided and fills the volume between a bearing housing 372 and the proximal portion 316. The bearing housing 372 facilitates rotation of the impeller shaft and the flow of infusate. The sleeve 368 has slots and/or other fluid communication structures formed therein that direct flow from channels in the catheter body 308 to flow channels in the bearing housing 372. In one embodiment, the sleeve 368 has a plurality of small apertures that are disposed between flow slots. The apertures and slots can be similar is shape and form to the apertures 224 and slots 220 discussed above.

In other embodiment, apertures can be formed in the bearing housing 372. For example, the bearing housing 372 can have a plurality of channels aligned with flow passages in the catheter body 304. In such embodiment, apertures for receiving the securement device 360 can be provided directly in the bearing housing 372. In another variation, apertures are provided that extend through the sleeve 368 and into the bearing housing 372.

Modifications of catheter pumps incorporating the catheter assembly 300 can be used for right side support. For example, the elongate body 304 can be formed to have a deployed shape corresponding to the shape of the vasculature traversed between a peripheral vascular access point and the right ventricle.

Any suitable manufacturing method can be used to cause a portion of the catheter body 304 to be disposed in the apertures 344. For example, in one the catheter body 304 and the cannula 308 are to be joined. The cannula 308 has the tubular portion 316 which is to be disposed over the catheter body 304. The ferrule 336 is a metallic body that is an important part of one form of a mechanical interface. The ferrule 336 has an inner surface and apertures 344 that act as a first interface zone and an outer surface that acts as a second interface zone. The ferrule 336 is positioned such that the inner surface is disposed over the outer surface of short length of the catheter body 304 adjacent to the distal end thereof.

In one technique, the outer surface of the catheter body 304 is mechanically coupled to the ferrule 336 by a process that involves heating. The distal portion of the catheter body 304 and the ferrule 336 are heated sufficiently to cause at least a portion of the catheter body to transition to a state with low resistance to deformation. The low resistance state can be a fluid state or just a state in which the material of the catheter body 304 if more malleable. In the state having low resistance to deformation, the catheter body 304 flows through or protrudes into the apertures 344. Because the material is formed continuously from a location inside the inner surface of the ferrule to outside the inner surface, a strong mechanical coupling is provided between these components.

The tubular portion 316 of the cannula 308 can be coupled with the ferrule 336 by any suitable technique. In one embodiment, the tubular portion 316 and the ferrule 336 are indirectly coupled through sleeve 368 discussed more below. In particular, the distal end of the ferrule 336 can be welded to the proximal end of the sleeve 368 and a second connection can be provided between the portion 316 and the sleeve as discussed elsewhere herein. In another embodiment, the ferrule 336 can be directly connected by a suitable technique, such as welding if suitable materials are provided. These structures are also illustrated in FIG. 16 below, which shows further details of the connection by the ferrule 336.

The foregoing technique of heating the catheter body 304 to cause the material thereof to be coupled with the proximal portion 160A of the pull wire(s) 160. Another technique for joining the pull wires 160 to the catheter body 304 is by an epoxy or other adhesive at the proximal end of the wires and/or catheter body 304. A distal section of the pull wires 160 within the catheter body 304 can be left un-adhered to the catheter body, such that this section of the pull wires 160 can move relative to the catheter body or “float” to enhance flexibility of the distal portion of the catheter body in some embodiments. The proximal portion 160A provides a first interface zone of a mechanical interface between the catheter body 104 and the bearing housing 146. The distal portion 160C provides a second interface zone that can be coupled with the bearing housing 146 by a suitable technique, such as welding. In another embodiment, the sleeve 216, 216A is formed of a material to which the pull wires can be welded or otherwise mechanically secured.

FIG. 11 illustrates an additional optional feature that can facilitate treatment with a catheter pump including the catheter assemblies disclosed herein or any of the pumps discussed in U.S. application Ser. Nos. 13/343,618 and 13/343,617, which are hereby incorporated herein by reference. A deployment system is provided by combining the catheter assembly 300 (or any other discussed or claimed herein) with a guide wire guide 240. The guide wire guide 240 can be configured as a small elongate tubular member sized to be advanced in a lumen formed in the drive shaft 144. The guide wire guide 240 includes a lumen that is sized to receive a guidewire (not shown). The wall thickness of the guide wire guide 240 is thin enough to fit within the allotted tolerance for tracking the catheter assemblies discussed herein through the vasculature. The guide wire guide 240 wall thickness is also thin enough to permit the guide wire guide 240 to be withdrawn from between the guide wire and the catheter assembly once the guidewire is in place without damaging either of these structures or disrupting the position of guidewire excessively. In various embodiments, the guide wire guide 240 includes a self healing member that remains within the catheter assembly when the tubular portion is removed. The self-healing member has an end wall that re-seals when the guidewire is removed. Thus, the guide wire guide 240 facilitates loading the catheter assemblies onto a guidewire for a percutaneous delivery within a patient.

FIGS. 15-17 show details of a catheter assembly 400 having a stator assembly 402 disposed in a distal portion thereof. The stator assembly 402 enhances the performance of a catheter pump including the catheter assembly 400. The stator assembly 402 can include a stator blade body 404 having one or a plurality of, e.g., three, blades 408 extending outwardly from a central boy 412. The stator blade body 404 is at a downstream location of the impeller 312. In a percutaneous left ventricle application, the stator blade body 404 is disposed proximal of the impeller 312. In a percutaneous right ventricle application, the stator blade body 404 is located distal of the impeller 312. In a transapical approach to aid the left ventricle, which might be provided through ports in the chest wall or via thoracotomy or mini-thoracotomy, the stator blade body 404 is disposed distal of the impeller 312.

The stator blades 408 are configured to act on the fluid flow generated by the impeller 312 to provide a more optimal fluid flow regime downstream of the stator assembly 402. This fluid flow regime can correspond to a more optimal fluid flow regime out of the outlet of the catheter pump. The stator blades 408 preferably convert at least the radial component of flow generated by the impeller 312 to a flow that is substantially entirely axial. In some cases, the stator blades 408 are configured to reduce other inefficiencies of the flow generated by the impeller 312, e.g., minimize turbulent flow, flow eddies, etc. Removing the radial components of the flow can be achieved with blades that are oriented in an opposite direction to the orientation of the blades of the impeller 312, for example, clockwise versus counterclockwise oriented blade surface.

While the stator blades 408 act on the flow generated by the impeller 312, the fluids also act on the stator assembly 402. For example, the stator blade body 404 experiences a torque generated by the interaction of the blades 408 with the blood as it flows past the stator assembly 402. A robust mechanical interface 420 is provided between the central body 412 and a distal portion of the catheter assembly 400. A bearing housing 424 is provided that is similar to the bearing housing 372, except as described differently below. The bearing housing 424 includes an elongate portion 428 that projects into a lumen of the central body 412. The elongate portion 428 preferably has an outer periphery that is smaller than an outer periphery of a portion of the bearing housing 424 immediately proximal of the elongate portion 428.

This structure provides an interface 432 disposed between the elongate portion and the portion just distal thereto. The interface 432 can be a shoulder having a radial extent that is approximately equal to that of the central body 412. In some embodiments, a flush surface is provided between the outer surface of the central body 412 and a distal outer surface of the sleeve 368 such that the radial extent of the shoulder of the interface 432 is less than that of the central body 412 by an amount approximately equal to the thickness of the sleeve 368. The interface 432 can also or alternately includes an engagement feature between the inner surface of the lumen of the central body 412 and the outer surface of the elongate portion 428. In one embodiment, the outer surface of the elongate portion 428 has a helical projection or groove and the central body 412 has corresponding and mating helical grooves or projections. These features can be or can be analogous to screw threads. Preferably the helix portion is arranged such that the torque felt by the stator assembly 402 generates a tightening of the engagement between the elongate portion 428 and the central body 412. The projections or grooves in the central body 412 can be formed by molding the central body 412 over the elongate projection 428.

A small gap is provided between the stator assembly 402 and the impeller 312 such that no or minimal contact is provided between these components, but the flow between the blades of these structures smoothly transitions between the blades thereof. Such an arrangement is useful in that the impeller 312 rotates at more than 10,000 RPM while the stator assembly 412 is stationary.

While the robust mechanical interfaces between the catheter body 104 and the cannula 108 is important to the catheter assembly 300 the interface is even more important in certain embodiments of the catheter body 400 that are actuated to a collapsed state prior to being removed from the patient. In such embodiments, the deployed working end preferably is collapsed, including the cannula 308, the stator blade body 404, and the impeller 312. This can be done by providing distal relative motion of the sheath assembly 88. The forces applied by the sheath assembly 88 to the catheter body 400, stator blade body 404, and the impeller 312 and focused at the mechanical joints are enhanced due to the presence of the stator blade body 404.

One will appreciate from the description herein that the catheter assembly may be modified based on the respective anatomy to suit the desired vascular approach. For example, the catheter assembly in the insertion state may be shaped for introduction through the subclavian artery to the heart. The catheter pump may be configured for insertion through a smaller opening and with a lower average flow rate for right side support. In various embodiments, the catheter assembly is scaled up for a higher flow rate for sicker patients and/or larger patients.

Although the inventions herein have been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present inventions. It is therefore to be understood that numerous modifications can be made to the illustrative embodiments and that other arrangements can be devised without departing from the spirit and scope of the present inventions as defined by the appended claims. Thus, it is intended that the present application cover the modifications and variations of these embodiments and their equivalents. 

1. A catheter pump assembly, comprising: a proximal portion; a distal portion; a catheter body having a lumen extending along a longitudinal axis between the proximal and distal portions; an impeller disposed at the distal portion; and a stator disposed at a downstream location of the impeller to straighten flow downstream from the impeller; wherein the stator is collapsible from a deployed configuration to a collapsed configuration.
 2. The catheter pump assembly of claim 1, wherein the stator is collapsible to a smaller diameter for percutaneous insertion.
 3. The catheter pump assembly of claim 1, wherein the stator is collapsible to a smaller diameter for insertion into a femoral artery.
 4. The catheter pump assembly of claim 1, further comprising a bearing assembly disposed proximal of the impeller, the stator being disposed on a distal projection of the bearing assembly.
 5. The catheter pump assembly of claim 4, wherein a mechanical interface is provided between the bearing assembly projection and the stator, the mechanical interface further comprising a distal facing radial shoulder adjacent to a proximal facing end of the stator.
 6. The catheter pump assembly of claim 4, wherein a mechanical interface is provided between the bearing assembly projection and the stator, the mechanical interface further comprising mating features disposed on the outer surface of the projection and on an inner surface of a lumen extending through a central body of the stator.
 7. The catheter pump assembly of claim 6, wherein the mating features comprise helical grooves and projections.
 8. The catheter pump assembly of claim 7, wherein the grooves and projections are configured to tighten engagement between the bearing assembly projection and the stator upon application of torque by fluid flow generated by the impeller.
 9. The catheter pump assembly of claim 1, wherein the stator is disposed proximal of the impeller in a percutaneous left ventricle application.
 10. The catheter pump assembly of claim 1, wherein the stator is disposed distal of the impeller in a percutaneous right ventricle application.
 11. The catheter pump assembly of claim 1, wherein the stator is disposed distal of the impeller in a transapical approach to aid the left ventricle.
 12. The catheter pump assembly of claim 1, wherein the stator comprises stator blades oriented in an opposite direction to an orientation of blades of the impeller.
 13. The catheter pump assembly of claim 1, wherein a gap is disposed between the stator and the impeller, the gap separating the stator and the impeller.
 14. The catheter pump assembly of claim 1, further comprising an elongate sheath body, wherein the sheath body is configured to apply force to the catheter body, the impeller, and the stator to facilitate collapsing of a deployed working end.
 15. A catheter system, comprising: an elongate polymeric catheter body comprising a proximal end and a distal end; a cannula having an expandable portion disposed distally of the elongate polymeric catheter body; at least one expandable component disposed within the cannula; and an elongate sheath body having a retracted position in which the elongate sheath body is proximal of the expandable portion of the cannula and the at least one expandable component and a forward position in which the elongate sheath body is disposed over the expandable portion of the cannula and the at least one expandable component; wherein a first segment of the elongate sheath body disposed over the expandable portion of the cannula and the at least one expandable component is configured to resist kinking to a greater extent than a second segment of the elongate sheath body disposed adjacent to the first segment.
 16. The catheter system of claim 15, wherein the first segment has a higher hardness than the second segment.
 17. The catheter system of claim 15, further comprising a stator disposed at a downstream location of the at least one expandable component to straighten flow downstream from the at least one expandable component, wherein the sheath body is configured to apply force to the catheter body, the cannula, the at least one expandable component, and the stator to facilitate collapsing of a deployed working end. 